1. Field of the Invention
The present invention is related to the fields of molecular biology, developmental biology, physiology, neurobiology and medicine. The invention provides polynucleotides encoding the zebrafish PTH1R receptor and polynucleotides for a novel zebrafish PTH3R receptor, as well as vectors and cells containing said polynucleotides. The invention further provides polypeptides for the PTH1R and PTH3R receptors. The polynucleotides and polypeptides of the invention are useful for the identification of agonist and antagonists of PTH1R or PTH3R receptor function and as reagents in the treatment of diseases or disorders associated with PTH1R or PTH3R function.
2. Related Art
The parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor (PTH1R) mediates in mammals and frogs the actions of PTH and PTHrP. Both peptides, most likely evolved through a gene duplication event from a common ancestral gene, and have retained limited homology within the amino-terminal region. Because of their structural conservation, PTH and PTHrP bind with similar affinity to the PTH1R, and activate this common receptor with similar or indistinguishable efficacy. Due to this unusual ligand-specificity, the PTH1R mediates the endocrine actions of PTH, the most important peptide regulator of calcium homeostasis in mammals, and the autocrine/paracrine actions of PTHrP, which is important for normal chondrocyte proliferation and differentiation (Karaplis, et al., (1997)); Lanske, et al., (1996)), and most likely for other, still incompletely defined functions including pancreas, skin, and breast development, as well as tooth eruption (Wysolmerski, et al., (1996)).
In addition to the PTH1R, a PTH type-2 receptor (PTH2R) has been isolated from mammals and teleosts (Usdin, et al., (1995); Rubin, et al. (1999)), and at least the human PTH2R is activated by PTH and a recently isolated hypothalamus peptide (Usdin, et al., (1999)). Its biological importance remains uncertain, as does the importance of additional receptors for which there is growing biological and pharmacological evidence. For example, receptors with specificity for amino-terminal PTH and PTHrP have been described for keratinocytes, squamous carcinoma cell lines, and central nervous system cells (Orloff et al., (1995 and 1996); Fukayama, et al., (1995)), and there is evidence for a PTHrP-selective receptor in the mammalian supraoptic nucleus (Yamamoto et al., (1997) and (1998)). In addition, the midregional portion of PTHrP stimulates an increase in intracellular free calcium in some cell lines and increases placental calcium transport (Kovacs et al., (1996); Wu et al., (1996); Orloffet al., (1996)), and the carboxy-terminal portion of PTH binds to a distinct receptor on clonal cell lines (Inomata, et al., (1995); Takasu, et al., (1998)).
Research on the parathyroid hormone (PTH) has been extensive. Formulations of PTH and compounds with PTH activity have been described (see U.S. Pat. Nos. 5,496,801; 5,814,603; 5,208,041;), and methods to produce the same are also known (see U.S. Pat. Nos. 5,616,560 and 5,010,010). In addition, analogs and inhibitors of PTH may be found in the prior art (see U.S. Pat. Nos. 4,423,037; 5,693,616; 5,695,955 and 5,798,225).
Thus, the invention furthers the art by focusing on PTH receptors and providing reagents and methods that are distinct and separate from PTH.